Braking stopping distance — Iowa Permit Test

The time it takes your wheels to stop depends on the vehicle's weight, size and load, and the condition of its tires.

Worn tires and a heavy load both make a car take longer to stop, so leave more room.

The time it takes your wheels to stop depends on the vehicle’s weight, size, and load, as well as the condition of its tires.

Braking too hard can make your vehicle skid on loose gravel, snow and ice, or even dry pavement.

Stomping on the brakes can lock the wheels, and a car with locked wheels slides instead of stopping.

Loose gravel roads, snow and ice, or even dry pavement may cause your vehicle to skid if the brakes are applied too hard.

At 20 mph, the manual's chart shows 44 feet of reaction distance plus 25 feet of braking distance: a stopping distance of 69 feet.

Your car keeps rolling while your foot moves to the brake. That reaction distance counts toward the stop.

At higher speeds, it takes longer to stop.

A vehicle traveling 60 mph travels 3 times farther before stopping than one traveling 30 mph.

Doubling your speed does far more than double your stop. That is why a fast car needs so much room.

For example, a vehicle traveling 60 mph will travel 3 times further than a vehicle traveling 30 mph before coming to a stop.

Which of these affects how long it takes your wheels to stop?

The condition of the car's tires. Worn tires and a heavy load both make a car take longer to stop, so leave more room. Iowa Driver's License Manual, p.40: “The time it takes your wheels to stop depends on the vehicle’s weight, size, and load, as well as the condition of its tires.”